1. Field of the Invention
This invention relates to an envelope signal generator for electronic musical instruments, in particular, a preset type music synthesizer (hereinafter referred to as the preset type synthesizer).
2. Description of the Prior Art
An envelope signal generator heretofore employed for electronic musical instruments is such, for example, as proposed in Japanese Patent Application No. 40317/76 filed by the assignee of the present application and now Laid-Open Patent Publication No. 124318/1977. With this conventional circuit, various envelopes can be obtained by varying each of attack, decay, sustain and release parts forming an envelope by operating a variable resistor or the like in accordance with a certain voltage value; however, this circuit is not suitable for use with the preset type synthesizer and the like for the following reason. Namely, in the preset type synthesizer, it is necessary to switch an envelope characteristic to a desired one immediately when selecting the kind of a note by a change-over, so that the circuit of the type changing the envelope characteristic by a variable resistor is not suited. To meet such a requirement, there have also been proposed circuits which employ many combinations of numbers of resistors, diodes and change-over switches and perform switching of the envelope characteristic by actuating a selected one of the change-over switches, but their circuit constructions become more and more complicated.
In musical instruments such as a piano and so forth, the envelope generally differs for the pitch of each note, whereas in the synthesizer, a pitch determining voltage signal is produced in accordance with the pitch of each note. Accordingly, it would be more effective if the envelope could be controlled by that voltage signal according to the pitch. Further, if the envelope could be controlled by a voltage value, this would bring about the advantage that remote control of the envelope signal generator can be achieved by connecting it with other devices.